Re: Excessive stall times on ext4 in 3.9-rc2

From: Frank Ch. Eigler
Date: Mon Apr 08 2013 - 06:54:30 EST

Hi, Mel -

> > [...] git kernel developers
> > should use git systemtap, as has always been the case. [...]
> At one point in the past this used to be the case but then systemtap had to
> be compiled as part of automated tests across different kernel versions. It
> could have been worked around in various ways or even installed manually
> when machines were deployed but generally took less time to
> keep working.

OK, if that works for you. Keep in mind though that newer versions of
systemtap retain backward-compatibility for ancient versions of the
kernel, so git systemtap should work on those older versions just

> [...]
> Yes, this was indeed the problem. The next version of
> treated get_request_wait() as a function that may or may not exist. It
> uses /proc/kallsyms to figure it out.

... or you can use the "?" punctuation in the script to have
systemtap adapt:

probe kprobe.function("get_request_wait") ? { ... }

- FChE
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